Method for producing polyglycerol (poly)carbonate

ABSTRACT

The invention relates to a method for producing a compound of fonnula (I), comprising the reaction, in the presence of a catalytic system comprising a single rare earth oxide or a mixture of rare earth oxides, of an alkyl carbonate or an alkylene carbonate with a polyol of fonnula (II), wherein p is a whole number between 2 and 10.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a U.S. national stage entry under 35 U.S.C.§371 of International Application No. PCT/EP2013/064595 filed Jul. 10,2013, which claims priority to FR Application No. 12.56678 filed on Jul.11, 2012, the whole content of this being herein incorporated byreference for all purposes.

The present invention relates to a method for producing polyglycerol(poly)carbonate.

Methods for the synthesis of glycerol carbonate are widely described inthe literature.

Methods applying organic carbonates have been developed.

A method for preparing glycerol carbonate by reaction of glycerol and ofa cyclic organic carbonate in the presence of a solid catalystcomprising a bicarbonated or hydroxylated anionic macroporous resin or athree dimensional zeolite of the X or Y type including basic sites at atemperature comprised between 50 and 110° C. is known notably from EP 0739 888. The yield of the reaction is of the order of 90%. In order toobtain this yield, it is however necessary to draw off the ethyleneglycol formed during the reaction. The method is applicable to pureglycerol as well as to glycerins.

A method for preparing glycerol carbonate by reaction between dimethylcarbonate and glycerol by transesterification catalysed by a lipase isalso known from US2010/0209979.

JP06329663 discloses a method for preparing glycerol carbonate byreaction between ethylene carbonate and glycerol catalyzed by aluminium,magnesium, zinc, titanium, lead oxides. Other methods were developed bycatalysis with CaO. However, these catalysts are not stable and arenotably degraded by water and do not give the possibility of conductingthe method continuously.

There exist other methods notably using phosgene and urea. The phosgenemethod, however, has the drawback of being highly toxic and is thereforenot suitable for preparing products entering the manufacturing of food,cosmetic or pharmaceutical compositions.

From EP 0 955 298, a method for synthesis of glycerol carbonate is thusknown, consisting in the reaction of glycerol with urea in the presenceof a catalyst of the metal or organometal salt type and having Lewisacid sites. The obtained molar yield is comprised between 40 and 80%relatively to glycerol.

However, the methods with urea generate ammonia in a strong proportion,this ammonia therefore has to be neutralized as a salt and these ammoniasalts are not recoverable. Drawbacks in terms of cost, difficulty ofpurification and sometimes observance of the environment (notablydischarge of dioxane and/or glycidol, use of glycidol, use of a catalystbased on tin, use of acetonitrile) are also described.

There is therefore a need to provide a method which may easily beindustrialized, which may be applied continuously and which does nothave any risk notably in terms of toxicity.

The present invention relates to a method for preparing bytranscarbonation a compound of formula (I)

wherein R¹ represents:

-   -   a (CH₂CH(OH)CH₂O)_(n)H group; or    -   a (CH₂CH(OH)CH₂O)_(m)CH₂R² group;        n representing an integer from 1 to 10, preferably from 1 to 5,        for example n represents 1 or 2;        m representing an integer from 0 to 10, preferably from 0 to 5,        for example m represents 0 or 1;        R² representing

said method comprises the reaction, in the presence of a catalyticsystem comprising as a catalytic entity a rare earth oxide alone or amixture of rare earth oxides, between an alkyl carbonate or an alkylenecarbonate and a polyol of formula (II)

wherein p represents an integer from 2 to 10.

In an embodiment, in the compound of formula (I) R¹ represents(CH₂CH(OH)CH₂O)_(n)H.

In another embodiment, in the compound of formula (I) R¹ represents(CH₂CH(OH)CH₂O)_(m)CH₂R².

Preferably, in the compound of formula (II) p represents an integer from2 to 5, preferably 2 or 3.

Within the scope of the present invention, the expression <<comprisedbetween x and y>> means that it also covers the limits x and y. Thus,<<comprised between x and y>> may be understood, within the scope of theinvention, as meaning <<ranging from x to y>>.

In the method according to the invention, the alkyl carbonate may be acompound of formula (III)

wherein R³ and R⁴, either identical or different, represent:

-   -   a linear or branched C₁-C₂₀ alkyl group;    -   a C₅-C₁₄, preferably C₆-C₁₄ aryl group; optionally substituted        with one or several substituents, notably selected from:        -   a C₁-C₉, preferably C₁-C₅ alkyl group;        -   a C₅-C₁₄, preferably C₆-C₁₄, preferably C₆-C₁₀ aryl group,            optionally substituted;        -   an alkyl-aryl group of formula -Q¹-Ar¹ wherein Q¹ represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar¹ represents a            C₆-C₁₄, preferably C₆ aryl group, optionally substituted;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₉, preferably C₁-C₅ alkoxy group;    -   a C₅-C₆ cycloalkyl group optionally substituted with one or        several substituents, notably selected from:        -   a C₁-C₉, preferably C₁-C₅ alkyl group;        -   a C₅-C₁₄, preferably C₆-C₁₄, preferably C₆-C₁₀ aryl group,            optionally substituted;        -   an alkyl-aryl group of formula -Q²-Ar² wherein Q² represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar² represents a            C₆-C₁₄, preferably C₆ aryl group, optionally substituted;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₉, preferably C₁-C₅ alkoxy group; or    -   a heteroaryl group, preferably comprising 5 to 10 members,        preferably comprising 1 to 2 heteroatoms, notably selected from        oxygen, nitrogen or sulfur; optionally substituted with one or        several substituents notably selected from:        -   a C₁-C₉, preferably C₁-C₅ alkyl group;        -   a C₅-C₁₄, preferably C₆-C₁₄, preferably C₆-C₁₀ aryl group,            optionally substituted;        -   an alkyl-aryl group of formula -Q³-Ar³ wherein Q³ represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar³ represents a            C₆-C₁₄, preferably C₆ aryl group, optionally substituted;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₉, preferably C₁-C₅ alkoxy group;    -   an alkyl-aryl group of formula -Q⁴-Ar⁴ wherein Q⁴ represents a        C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁴ represents a        C₆-C₁₄, preferably C₆ aryl group, optionally substituted.

Preferably in the method of the invention, R³ and R⁴, either identicalor different, represent:

-   -   a linear or branched C₁-C₁₀ alkyl group, for example a methyl,        ethyl, propyl, butyl;    -   a C₆, C₁₀ or C₁₄ aryl group, optionally substituted with one or        several substituents, notably selected from:        -   a C₁-C₅ alkyl group, for example methyl, ethyl; a phenyl            group, optionally substituted;        -   an alkyl-aryl group of formula -Q¹-Ar¹ wherein Q¹ represents            a C₁-C₉ preferably C₁-C₅ alkyl radical and Ar¹ represents a            phenyl group optionally substituted, preferably a            methylphenyl, ethylphenyl;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₅ alkoxyl group, for example a methoxy, ethoxy;    -   a C₅-C₆ cycloalkyl group optionally substituted with one or        several substituents, notably selected from:        -   a C₁-C₅ alkyl group, for example a methyl, ethyl; a phenyl            group optionally substituted;        -   an alkyl-aryl group of formula -Q²-Ar² wherein Q² represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar² represents a            phenyl group optionally substituted, preferably a            methylphenyl, ethylphenyl;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₅ alkoxy group, for example a methoxy, ethoxy; or    -   a heteroaryl group preferably comprising 5 to 10 members,        preferably comprising 1 to 2 heteroatoms, notably selected from        oxygen, nitrogen or sulfur, for example aniline, optionally        substituted with one or several substituents, notably selected        from        -   a C₁-C₅ alkyl group, for example a methyl, ethyl; a phenyl            group optionally substituted;        -   an alkyl-aryl group of formula -Q³-Ar³ wherein Q³ represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar³ represents a            phenyl group optionally substituted, preferably a            methylphenyl, ethylphenyl;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₅ alkoxy group, for example a methoxy, ethoxy;    -   an alkyl-aryl group of formula -Q⁴-Ar⁴ wherein Q⁴ represents a        C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁴ represents a        phenyl group optionally substituted.

Advantageously, the alkyl carbonate is dimethyl carbonate, diethylcarbonate. Preferably, the alkyl carbonate is dimethyl carbonate.

According to the invention, by an alkylene carbonate is meant a compoundof formula (IV)

whereinR⁵, R⁶, R⁷ and R⁸ either identical or different are selected from:

-   -   a hydrogen;    -   a linear, branched or cyclic C₁-C₉, preferably C₁-C₅ hydrocarbon        group which may comprise one or several heteroatoms, notably        selected from oxygen, nitrogen or sulfur, and may comprise one        or several substituents OH;    -   a group of formula —CH₂—R¹⁰, wherein R¹⁰ represents a linear,        branched or cyclic C₁-C₉, preferably C₁-C₅ hydrocarbon group        which may comprise one or several heteroatoms, notably selected        from oxygen, nitrogen or sulfur, and may comprise one or several        substituents OH;    -   a group of formula C(O)OR¹¹, wherein R¹¹ represents a hydrogen        atom, a C₁-C₉, preferably C₁-C₅ alkyl group for example a        methyl, ethyl;    -   a C₅-C₆ cycloalkyl group optionally substituted with one or        several substituents notably selected from:        -   a C₁-C₉, preferably C₁-C₅ alkyl group; a C₅-C₁₄, preferably            C₆-C₁₄, preferably C₆-C₁₀ aryl group, optionally            substituted;        -   an alkyl-aryl group of formula -Q⁵-Ar⁵ wherein Q⁵ represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁵ represents a            C₆-C₁₄, preferably C₆ aryl group, optionally substituted;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₉, preferably C₁-C₅ alkoxy group;    -   a heteroaryl group, preferably comprising 5 to 10 members,        preferably comprising 1 to 2 heteroatoms, notably selected from        oxygen, nitrogen or sulfur optionally substituted with one or        several substituents notably selected from:        -   a C₁-C₉, preferably C₁-C₅ alkyl group; a C₅-C₁₄, preferably            C₆-C₁₄, preferably C₆-C₁₀ aryl group, optionally            substituted;        -   an alkyl-aryl group of formula -Q⁶-Ar⁶ wherein Q⁶ represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁶ represents a            C₆-C₁₄, preferably C₆ aryl group, optionally substituted;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein n            represents an integer comprised between 2 and 5 and R¹⁵            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₉, preferably C₁-C₅ alkoxy group;    -   a C₆-C₁₄ aryl group, optionally substituted with one or several        substituents, notably selected from:        -   a C₁-C₉, preferably C₁-C₅ alkyl group; a C₅-C₁₄, preferably            C₆-C₁₄, preferably C₆-C₁₀ alkyl group, optionally            substituted;        -   an alkyl-aryl group of formula -Q⁷-Ar⁷ wherein Q⁷ represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁷ represents a            C₆-C₁₄, preferably C₆ aryl group, optionally substituted;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁ C₅ alkyl group;        -   a C₁-C₉, preferably C₁-C₅ alkoxy group;    -   an alkyl-aryl group of formula -Q⁸-Ar⁸ wherein Q⁸ represents a        C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁸ represents a        C₆-C₁₄, preferably C₆ aryl group, optionally substituted;        or one of the R⁵/R⁶ and one of the R⁷/R⁸ form together with the        carbon atoms which bear them a double bond; or one of the R⁵/R⁶        and one of the R⁷/R⁸ form together with the carbon atoms bearing        them a double bond which is comprised in an aryl, notably phenyl        group, formed by R⁶ and R⁷ with the two carbon atoms bearing        them.

Preferably in the method of the invention R⁵, R⁶, R⁷ and R⁸, eitheridentical or different are selected from:

-   -   a hydrogen;    -   a linear or branched C₁-C₉, preferably C₁-C₅ alkyl group which        may comprise one or several heteroatoms, notably selected from        oxygen, nitrogen or sulfur, and may comprise one or several        substituents OH; for example methylene, ethylene;    -   a group of formula —CH₂—R¹⁰, wherein R¹⁰ represents a linear or        branched C₁-C₅ hydrocarbon group which may comprise one or        several heteroatoms, notably selected from oxygen, nitrogen or        sulfur and may comprise one or several substituents OH, for        example ethylene, methylene;    -   a group of formula C(O)OR¹¹, wherein R¹¹ represents a hydrogen        atom, a C₁-C₅ alkyl group, for example a methyl, ethyl;    -   a C₅-C₆ cycloalkyl group optionally substituted with one or        several substituents notably selected from:        -   a C₁-C₅ alkyl group, for example methyl, ethyl; a phenyl            group optionally substituted;        -   an alkyl-aryl group of formula -Q⁵-Ar⁵ wherein Q⁵ represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁵ represents a            phenyl group optionally substituted, preferably            methylphenyl, ethylphenyl;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₅ alkoxy group, for example a methoxy, ethoxy;    -   a heteroaryl group, preferably comprising 5 to 10 members,        preferably comprising 1 to 2 heteroatoms, notably selected from        oxygen, nitrogen or sulfur, for example aniline, optionally        substituted with one or several substituents, notably selected        from:        -   a C₁-C₅ alkyl group, for example a methyl, ethyl; a phenyl            group optionally substituted;        -   an alkyl-aryl group of formula -Q⁶-Ar⁶ wherein Q⁶ represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁶ represents a            phenyl group optionally substituted, preferably a            methylphenyl, ethylphenyl;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₅ alkoxy group, for example a methoxy, ethoxy;    -   a C₆, C₁₀ or C₁₄ aryl group, optionally substituted with one or        several substituents notably selected from:        -   a C₁-C₅ alkyl group, for example a methyl, ethyl;        -   a phenyl group optionally substituted; an alkyl-aryl group            of formula -Q⁷-Ar⁷ wherein Q⁷ represents a C₁-C₉, preferably            C₁-C₅ alkyl radical and Ar⁷ represents a phenyl group            optionally substituted, preferably a methylphenyl,            ethylphenyl;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₅ alkoxy group, for example a methoxy, ethoxy;    -   an alkyl-aryl group of formula -Q⁸-Ar⁸ wherein Q⁸ represents a        C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁸ represents an        optionally substituted phenyl;        or one of the R⁵/R⁶ and one of the R⁷/R⁸ form together with the        carbon atoms bearing them a double bond; or one of the R⁵/R⁶ and        one of the R⁷/R⁸ form together with the carbon atoms bearing        them a double bond which is comprised in an aryl group, notably        phenyl, formed by R⁶ and R⁷ with the two carbon atoms bearing        them.

Advantageously, the alkyl carbonate may be ethylene carbonate, propylenecarbonate, dibutylene carbonate or dihexylene carbonate.

According to the invention, the catalytic system comprises as acatalytic entity, a rare earth oxide or a mixture of rare earth oxides.

In an embodiment of the invention, the catalytic system consists of acatalytic entity selected from rare earth oxides or mixtures thereof.

By rare earth (Ln), are meant chemical elements selected from the groupformed by scandium, yttrium and chemical elements with an atomic numberfrom 57 to 71. Advantageously, the rare earths are selected from cerium(Ce), lanthanum (La), praseodymium (Pr), neodymium (Nd), yttrium (Y),gadolinium (Gd), samarium (Sm) and holmium (Ho), alone or as a mixture,preferably cerium, lanthanum, praseodymium, samarium, yttrium andneodymium, or mixtures thereof.

According to the invention, the rare earth oxides are selected fromCeO₂; Pr₆O₁₁, rare earth oxides of formula Ln₂O₃ wherein Ln representslanthanum, neodymium, yttrium, gadolinium, samarium or holmium; alone oras a mixture.

Advantageously, the rare earth oxides are selected from La₂O₃, CeO₂,Pr₆O₁₁, Nd₂O₃, Sm₂O₃, Y₂O₃, alone or as a mixture, preferably La₂O₃. Asa particular mixture, mention may for example be made of CeO₂/Pr₆O₁₁.

Preferably, the rare earth oxide is La₂O₃.

Preferably, the rare earth oxide is CeO.

Generally, the catalytic system according to the invention consists of acatalytic entity in solid form, thereby allowing its use in a continuousmethod. The catalyst may notably be found in monolithic form (forming asingle inert, rigid, porous block) or in an extruded form.

The catalytic system may also comprise an inert support on which isdeposited the catalytic entity. The catalytic system comprising asupport according to the invention may be in an extruded form, in theform of a coating having catalytic properties and based on a rare earthoxide or on a mixture of rare earth oxides and optionally of a binder ofa known type on a substrate of the monolithic metal or ceramic type.Advantageously, it is in an extruded form. The extruded formadvantageously gives the possibility of shaping the method of theinvention continuously, which is not possible with a powder catalystwhich would obstruct the different elements of the reactor.

For the method according to the invention, by extruded catalytic systemis meant any catalytic system obtained by ejection under pressure of aslurry through nozzles or dies of selected shapes. The thereby obtainedcatalytic systems may have various forms, they may for example havecylindrical or half-cylindrical, square, polygonal sections or furthersections in the form of lobes, such as tri-lobes. The catalytic systemsmay be solid or hollow, they may have the form of a monolith or of ahoneycomb. These extruded catalytic systems may notably be obtained bythe method as described on pages 4 to 10 of the patent applicationWO98/24726.

By inert support is meant a support which does not come into play, as acatalyst or as a reagent, in the transcarbonation reaction of theinvention and this regardless of the pH. Typically, the support isneutral, i.e. it does not substantially modify the catalytic activity ofthe catalytic entity. The support may also be described as inactive inso far that it does not have any catalytic activity for the reaction anddoes not modify the catalytic activity of the catalytic entity. Thesupports are selected from extrudable and non-hydrolyzable supports ormonolithic and non-hydrolyzable supports.

Preferably, the support may be selected from extrudable andnon-hydrolyzable metal oxides, clays, active coals (black coals),ceramic or metal monoliths.

The support may for example be selected from titanium oxides, zirconiumoxides, iron oxides; aluminium oxides, notably alundum; silica-alumina,for example clays; active coals; Kieselguhr.

This may also be corundum, silica carbide, pumice.

Among extrudable and non-hydrolyzable metal oxides, mention maypreferably be made of titanium oxides, zirconium oxides, iron oxides,aluminium oxides, preferably titanium oxides, zirconium oxides, neutralalumina. More preferably, the support is selected from titanium oxides,zirconium oxides, iron oxides, aluminium oxides, notably neutralalumina, active coals preferably titanium oxides, zirconium oxides,neutral aluminas, active coals.

The amount of catalytic entity on the support may be comprised between0.05 to 25% by mole based on the number of moles of the support,preferably from 1 to 10% molar. It should be noted that this valuenotably depends on the nature of the support, on its specific surfacearea, on its porosity and on the desired catalytic properties.

According to the invention, the catalytic system may notably have aspecific surface area of at least 1 m²/g, preferably the specificsurface area is comprised between 1 and 150 m²/g, more preferentiallycomprised between 3 and 100 m²/g. One skilled in the art is able toadjust this specific surface area for example by calcination of thecatalytic system.

According to the invention, the catalytic system may be doped withmetals of the Lewis acid type, for example transition metals,earth-alkaline metals and metalloids. Advantageously, these catalyticentities form with the dopants solid solutions forming an entity unit.

These metals may be selected from iron (Fe^(II) and Fe^(III)), copper(Cu^(I) and Cu^(II)), aluminium (Al^(III)), titanium (Ti^(IV)), boron(B^(III)), zinc (Zn^(II)) and magnesium (Mg^(II)). Preferably thesemetals are selected from the group formed by iron (Fe^(II) andFe^(III)), copper (Cu^(I) and Cu^(II)), titanium (Ti^(IV)) and zinc(Zn^(II)).

In the method of the invention, the relative percentage of metalrelatively to the catalytic entity may be comprised between 0.01 and 10%by moles, preferably between 1 and 10% by moles, for example between 1and 5% by moles.

Advantageously, the catalytic systems of the invention are stabletowards water. For example the catalysts of the invention may containless than 5% by weight of water. This advantageously gives thepossibility of conducting the transcarbonation reaction in a mediumcontaining water, for example in a medium containing less than 15% byweight of water, for example less than 5% by weight of water. Thus, andunlike the method of the state of the art, it is not necessary to havesignificant control of the amount of water in the reaction medium and itis not necessary to apply reagents free of water. This notably hasadvantages in terms of costs.

The catalyst according to the invention may advantageously be easilyrecovered after reaction with any method known to one skilled in theart, notably by decantation or filtration.

The method according to the invention is conducted at atmosphericpressure or autogenous pressure.

By autogenous pressure is meant the pressure inside the reactor which isdue to the reagents used. In the case of the present invention, byautogenous pressure is meant a pressure of less than 1 MPa, preferablyless than 0.5 MPa, preferably less than 0.3 MPa, for example less than0.2 MPa.

According to the invention, the method according to the invention isapplied at a temperature comprised between 25 and 250° C., preferablybetween 25 and 200° C., for example between 50 and 125° C.

Advantageously, the polyol/alkyl carbonate or polyol/alkylene carbonatemolar ratio is comprised between 1/30 and 1/1, preferably between 1/20and 1/1, for example between 1/15 and 1/1.

Advantageously, the polyol/alkyl carbonate or polyol/alkylene carbonatemolar ratio is comprised between 1/30 and 1/10, preferably between 1/30and 1/15 and the compound of formula (I) is a compound in which R¹represents (CH₂CH(OH)CH₂O)_(m)CH₂R².

Advantageously, the polyol/alkyl carbonate or polyol/alkylene carbonatemolar ratio is comprised between 1/8 and 1/1, preferably between 1/5 and1/1 and the compound of formula (I) is a compound in which R¹ represents(CH₂CH(OH)CH₂O)_(n)H.

Advantageously, the amount of catalytic entity is comprised between 0.01and 50% molar based on the number of moles of polyol, preferably between1 and 25% molar, preferably between 3 and 15% molar.

The method according to the invention gives the possibility of obtainingthe compound of formula (I) with good yields.

Advantageously, the method according to the invention is applied in theabsence of a solvent. The polyol may be used as a solvent in thereaction according to the invention.

The method according to the invention may be applied continuously orbatch wise. Advantageously, the method according to the invention isapplied continuously.

According to the invention, the method may comprise a preliminary stepfor preparing an alkyl carbonate or an alkylene carbonate. Thispreliminary step is achieved by reaction between an alcohol or a mixtureof alcohols or a diol and CO₂, in the presence of a catalytic systemconsisting of a catalytic entity selected from rare earth oxides andmixtures of rare earth oxides and optionally of a support.

The catalytic entity and the support are as defined for thetranscarbonation method according to the invention.

Advantageously, the molar ratio between alcohol or diol and CO₂ iscomprised between 1 and 150 equivalents in moles, preferably between 1and 100 equivalents.

According to the invention, the preliminary step for preparing an alkylcarbonate or an alkylene carbonate is applied at an autogenous pressureor at atmospheric pressure.

According to the invention, the preliminary step for preparing an alkylcarbonate or an alkylene carbonate is applied at a temperature comprisedbetween 25 and 250° C., preferably between 25 and 200° C., for examplebetween 50 and 150° C.

Advantageously, the amount of catalytic system is comprised between 0.01and 50% by mass based on the weight of alcohol, of a mixture of alcoholsor of diol, preferably between 1 and 25% by mass, preferably between 3and 15% by mass.

According to the invention, the alcohol fits the formula R¹²OH whereinR¹² represents:

-   -   a linear or branched C₁-C₂₀ alkyl group;    -   a C₅-C₁₄ aryl group optionally substituted with one or several        substituents, notably selected from:        -   a C₁-C₉, preferably C₁-C₅ alkyl group;        -   a C₅-C₁₄, preferably C₆-C₁₄, preferably C₆-C₁₀ aryl group,            optionally substituted;        -   an alkyl-aryl group of formula -Q¹-Ar¹ wherein Q¹ represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁹ represents a            C₆-C₁₄, preferably C₆ aryl group, optionally substituted;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein n            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₉, preferably C₁-C₅ alkoxy group;    -   a C₅-C₆ cycloalkyl group optionally substituted with one or        several substituents notably selected from:        -   a C₁-C₉, preferably C₁-C₅ alkyl group;        -   a C₅-C₁₄, preferably C₆-C₁₄, preferably C₆-C₁₀ aryl group,            optionally substituted;        -   an alkyl-aryl group of formula -Q²-Ar² wherein Q² represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar² represents a            C₆-C₁₄, preferably C₆ aryl group, optionally substituted;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₉, preferably C₁-C₅ alkoxy group; or    -   a heteroaryl group, preferably comprising 5 to 10 members,        preferably comprising 1 to 2 heteroatoms, notably selected from        oxygen, nitrogen or sulfur; optionally substituted with one or        several substituents, notably selected from:        -   a C₁-C₉, preferably C₁-C₅ alkyl group;        -   a C₅-C₁₄, preferably C₆-C₁₄, preferably C₆-C₁₀ aryl group,            optionally substituted;        -   an alkyl-aryl group of formula -Q³-Ar³ wherein Q³ represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar³ represents a            C₆-C₁₄, preferably C₆ aryl group, optionally substituted;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₉, preferably C₁-C₅ alkoxy group;    -   an alkyl-aryl group of formula -Q⁴-Ar⁴ wherein Q⁴ represents a        C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁴ represents a        C₆-C₁₄, preferably C₆ aryl group, optionally substituted.

Preferably in the method of the invention, R¹² represents:

-   -   a linear or branched C₁-C₁₀ alkyl group, for example a methyl,        ethyl, propyl, butyl;    -   a C₆, C₁₀ or C₁₄ aryl group, optionally substituted with one or        several substituents, notably selected from:        -   a C₁-C₅ alkyl group, for example methyl, ethyl; a phenyl            group, optionally substituted;        -   an alkyl-aryl group of formula -Q¹-Ar¹ wherein Q¹ represents            a C₁-C₉ preferably C₁-C₅ alkyl radical and Ar¹ represents a            phenyl group optionally substituted, preferably a            methylphenyl, ethylphenyl;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₅ alkoxy group, for example a methoxy, ethoxy;    -   a C₅-C₆ cycloalkyl group optionally substituted with one or        several substituents, notably selected from:        -   a C₁-C₅ alkyl group, for example a methyl, ethyl; a phenyl            group optionally substituted;        -   an alkyl-aryl group of formula -Q²-Ar² wherein Q² represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar² represents a            phenyl group optionally substituted, preferably a            methylphenyl, ethylphenyl;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₅ alkoxy group, for example a methoxy, ethoxy; or    -   a heteroaryl group preferably comprising 5 to 10 members,        preferably comprising 1 to 2 heteroatoms, notably selected from        oxygen, nitrogen or sulfur, for example aniline, optionally        substituted with one or several substituents, notably selected        from:        -   a C₁-C₅ alkyl group, for example a methyl, ethyl; a phenyl            group optionally substituted;        -   an alkyl-aryl group of formula -Q³-Ar³ wherein Q³ represents            a C₁-C₉, preferably C₁-C₅ alkyl radical and Ar³ represents a            phenyl group optionally substituted, preferably a            methylphenyl, ethylphenyl;        -   a polyalkoxy group of formula —(OCH₂CH₂)_(q)—OR⁹ wherein q            represents an integer comprised between 2 and 5 and R⁹            represents a C₁-C₁₀, preferably C₁-C₅ alkyl group;        -   a C₁-C₅ alkoxy group, for example a methoxy, ethoxy;    -   an alkyl-aryl group of formula -Q⁴-Ar⁴ wherein Q⁴ represents a        C₁-C₉, preferably C₁-C₅ alkyl radical and Ar⁴ represents a        phenyl group optionally substituted.

According to the invention, the diol fits the formula (V)

wherein

R⁵, R⁶, R⁷ and R⁸ either identical or different are as defined earlier.

By a continuous method is meant a method in which the reagents arebrought continuously into the reactor and the products are drawn offfrom the reaction medium, continuously and then separated. The unreactedreagents may be reintroduced into the reaction medium or else removed.

The invention will now be described by means of examples, the latterbeing given as an illustration without however being limiting.

EXAMPLE 1 Synthesis of Diglycerol Monocarbonate

In a 50 ml flask, provided with a condenser, 7 g (42 mmol) of diglycerol(purity ≧80%) and 15.2 g (168 mmol) of dimethyl carbonate areintroduced. The mixture is then brought to 90° C. and 0.7 g (2.1 mmol, 5mol %) of lanthanide oxide are added. The reaction medium is heated to120° C. for 24 hours. The solution is then filtered. After evaporationof dimethyl carbonate, the obtained product is purified by achromatographic column on a flash silica column (Eluent(dichloromethane/MeOH: 9/1)) in order to obtain diglycerol monocarbonate with an isolated yield of 81% and diglycerol dicarbonate withan isolated yield of 19%.

EXAMPLE 2 Synthesis of Triglycerol Monocarbonate

In a 50 ml flask, provided with a condenser, 7 g (29 mmol) oftriglycerol and 10.5 g (116 mmol) of dimethyl carbonate are introduced.The mixture is then brought to 90° C. and 0.47 g (1.5 mmol, 5 mol %) oflanthanide oxide are added. The reaction medium is heated to 120° C. for24 hours. The solution is then filtered. After evaporation of dimethylcarbonate, the obtained product is purified by a chromatographic columnon a flash silica column (eluent (dichloromethane/MeOH: 9/1)) in orderto obtain triglycerol monocarbonate with an isolated yield of 80% andtriglycerol dicarbonate with an isolated yield of 20%.

EXAMPLE 3 Synthesis of Diglycerol Dicarbonate

In a 100 ml flask, provided with a condenser, 5 g (30 mmol) ofdiglycerol (purity 80%) and 40.7 g (450 mmoles) of dimethyl carbonateare introduced. The mixture is then brought to 90° C. and 0.5 g (1.5mmol, 5 mol %) of lanthanide oxide are added. The reaction medium isheated to 120° C. for 48 hours. The solution is then filtered. Afterevaporation of dimethyl carbonate, the product is crystallized frommethanol in order to obtain after filtration of the solution, diglyceroldicarbonate with an isolated yield of 90%.

The following table groups the results of the different applied tests.

Conversion in Isolated yield Inlet Catalyst Obtained products % in % 1

81 La₂O₃ — >99 —

19 2

80 La₂O₃ — >99 —

20 3 La₂O₃

>99 90

The method according to the invention therefore gives the possibility ofobtaining in a simple and efficient way polyglycerol (poly)carbonates.

The invention claimed is:
 1. A method for preparing by transcarbonationof a compound of formula (I),

wherein R¹ represents: a (CH₂CH(OH)CH₂O)_(n)H group; or a(CH₂CH(OH)CH₂O)_(m)CH₂R² group; n representing an integer from 1 to 10;m representing an integer from 0 to 10; R² representing

said method comprising the reaction, in the presence of a catalyticsystem comprising as a catalytic entity selected from a group consistingof a rare earth oxide alone and a mixture of rare earth oxides, betweenan alkyl carbonate or an alkylene carbonate and a polyol of formula (II)

wherein p represents an integer from 2 to
 10. 2. The method according toclaim 1 wherein the alkyl carbonate is a compound of formula (III):

wherein R³ and R⁴, either identical or different, represent: a linear orbranched C₁-C₂₀ alkyl group; a C₅-C₁₄ aryl group; a C₅-C₆ cycloalkylgroup; or a heteroaryl group; an alkyl-aryl group of formula -Q⁴-Ar⁴wherein Q⁴ represents a C₁-C₉ alkyl radical and Ar⁴ represents a C₆-C₁₄aryl group.
 3. The method according to claim 1 wherein the alkylenecarbonate is a compound of formula (IV)

wherein R⁵, R⁶, R⁷ and R⁸ either identical or different are selectedfrom: a hydrogen; a linear, branched or cyclic C₁-C₉ hydrocarbon groupwhich may have one or several heteroatoms, and may have one or severalsubstituents OH; a group of formula —CH₂—R¹⁰, wherein R¹⁰ represents alinear, branched or cyclic C₁-C₉ hydrocarbon group which may have one orseveral heteroatoms, and may have one or several substituents OH; agroup of formula C(O)OR¹¹, wherein R¹¹ represents a hydrogen atom, aC₁-C₉ alkyl group; a C₅-C₆ cycloalkyl group; a heteroaryl group; aC₆-C₁₄ aryl group; an alkyl-aryl group of formula -Q⁸-Ar⁸ wherein Q⁸represents a C₁-C₉ alkyl radical, and Ar⁸ represents a C₆-C₁₄ arylgroup; or one of the R⁵/R⁶ and one of the R⁷/R⁸ form together with thecarbon atoms bearing them a double bond; or one of the R⁵/R⁶ and one ofthe R⁷/R⁸ form together with the carbon atoms bearing them a double bondwhich is comprised in an aryl group formed by R⁶ and R⁷ with the twocarbon atoms bearing them.
 4. The method according claim 1 wherein R¹represents (CH₂CH(OH)CH₂O)_(n)H.
 5. The method according to claim 1wherein R′ represents (CH₂CH(OH)CH₂O)_(m)CH₂R².
 6. The method accordingto claim 1 wherein the rare earth oxides fit the formula Ln₂O₃, with Lnrepresenting lanthanum, neodymium, yttrium, gadolinium, samarium orholmium; CeO₂ or Pr₆O₁₁, alone or as a mixture.
 7. The method accordingto claim 6, wherein the rare earth oxides are selected from La₂O₃, CeO₂,Pr₆O₁₁, Nd₂O₃, Sm₂O₃, Y₂O₃, alone or as a mixture.
 8. The methodaccording to claim 1 wherein the catalytic system comprises an inertsupport selected from the group consisting of extrudable andnon-hydrolyzable metal oxides, clays, active coals (black coals),ceramic monoliths, and metal monoliths.
 9. The method according to claim1 wherein the catalytic system is extruded.
 10. The method according toclaim 1 wherein the polyol/alkyl carbonate or polyol/alkylene carbonatemolar ratio is comprised between 1/30 and 1/10.
 11. The method accordingto claim 1 wherein the polyol/alkyl carbonate or polyol/alkylenecarbonate molar ratio is comprised between 1/8 and 1/1.
 12. The methodaccording to claim 1, wherein the amount of catalytic entity iscomprised between 0.01 and 50% molar based on the number of moles ofpolyol.
 13. The method according to claim 1, applied continuously. 14.The method according to claim 1, wherein the polyol/alkyl carbonate orpolyol/alkylene carbonate molar ratio is comprised between 1/30 and1/15.
 15. The method according to claim 1, wherein the polyol/alkylcarbonate or polyol/alkylene carbonate molar ratio is comprised between1/5 and 1/1.
 16. The method according to claim 1, wherein the amount ofcatalytic entity is comprised between 1 and 25% molar based on thenumber of moles of polyol.
 17. The method according to claim 1, whereinthe amount of catalytic entity is comprised between 3 and 15% molarbased on the number of moles of polyol.